Silver is guest editor of a special issue of the journal American Psychologist devoted entirely to assessing the psychological aftermath of the attacks.

The consequences, Silver writes, â€œshattered a sense of security and perceptions of invulnerability.â€

What does that do to us personally? Are we fearful?

It made me anxious as my daughter left California to attend NYU in 2006, and it was never far from my mind when I visited and looked out her window to the scar that had been the World Trade Center.

It continues to make me low-grade anxious that my daughter lives in Manhattan and my son in Washington, D.C. â€“ but not so anxious I am in a fever of fear.

As the song says: The world keeps revolving. And the ability to acknowledge and adapt â€“ an ability most of us possess â€“ might be the most positive conclusion Silver shares.

The Sept. 11 attack was unique in many ways, including its size and scope.

It also was the biggest terror attack to play out on live television. About 60 percent of the U.S. population was watching on television when the planes hit, or when the towers fell.

â€œPeople saw it live unfolding before their eyes,â€ Silver says.

And, she adds, that matters.

â€œPeople who saw the attack live had a stronger reaction than those who learned later.â€

Today, thousands of images go viral on the Internet. But 10 years ago we had little experience with that instant, collective impact. Silver says schoolchildren in London and pregnant women in the Netherlands suffered emotional or physical effects as a result of watching 9/11 unfold on TV.

Silver and her colleague conducted two studies tracking the mental and physical health of individuals in the wake of 9/11 and found that the impact extended well beyond just those directly exposed to or affected by the attacks.

For the first time, she says, television watching was linked to post-traumatic stress disorder.

The finding was unexpected, Silver explains, because a basic criterion of PTSD is direct exposure to the trauma.

â€œThe symptoms that were assumed to require direct exposure were now being seen by people who had merely learned about the attacks by television â€¦ . It was not anticipated that PTS symptoms would turn up in Kansas.â€

Watching over and over in horrid fascination does no good, she says.

â€œThere is no benefit in continuing to watch graphic images of the attack. I saw no benefits 24 hours later.â€

On 9/11, Silver’s son was 6 and her stepdaughter 13.

â€œI remember when the attacks happened, I called my son into the bedroom to see it on television. I told him this is an important day â€¦ I talked a lot about it with them.â€

She watched on television as the buildings fell and she did not watch again.

Silver’s research focuses on how individuals cope with traumatic loss.

She was motivated after a high school friend lost her father quickly to a brain tumor.

â€œI didn’t have a way of helping her.â€

Gradually, her focus evolved from personal loss to natural disasters such as the Northridge earthquake and then to collective traumas such as the Columbine High School shootings.

Since 2003 Silver has advised the Department of Homeland Security about the psychological impact of disasters: how to communicate effectively before and after an event.

In the case of 9/11, Silver found that as of four years ago 95 percent of those with indirect exposure no longer experience symptoms.

â€œExcept for those who suffered a direct loss, the psychological consequences have not been long-lasting in general.â€

What’s left, of course, might be a different view of the world and feelings of vulnerability.

â€œThere’s a recognition that it could happen again. On Sept. 10, 2001, no one thought it would happen. On Sept. 10, 2011, we think it could happen.â€

For children, the level of fear depends on their parents. Turns out kids are something like Silly Putty â€“ picking up the attitudes and anxiety around them.

As adults, we have come to accept that our world is more dangerous. It was already different from the days when we played outside until dark and our parents never looked for us until dinnertime.

Silver remembers she felt quite comfortable allowing her stepdaughter to fly to Chicago alone at age 11.

â€œWhen my son was 10 in 2004, I wouldn’t have dared allowed him to go on an airplane alone. We were sensitive to airplanes being used as bombs.â€

The old world is gone and we’re left with something different.

â€œWe accept and acknowledge that’s the world we live in. In order to be safe, we have to take off our shoes at the airport.

â€œAre we distressed? In general: No. Are we accepting the changed world as a result? Yes.â€

So how should we mark this 10th anniversary?

â€œI don’t see the value of showing those photos again â€¦ . One can respectfully acknowledge the loss without re-traumatizing people.â€

For those who lost a loved one, clearly the long-term impact is entirely different. But for the rest of society, Silver says, we are no longer experiencing distress.

And yet:

â€œWe aren’t where we were before the attacks.â€

I offer some labels for her to try on, suggesting â€œrecoveringâ€ or â€œmoving on.â€

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